Isolation of N epsilon-(gamma-glutamyl) lysine from polymers unique for cataract (Lorand et al., PNAS 78, 1356, 1981) was the spur for current efforts to investigate in greater depth the role of the protein cross-linking enzyme: transglutaminase in lens aging. The present five-year proposal represents a combination of this promising novel approach for exploring specific post-translational modifications of proteins in the aging human lens, progressing towards cataract, and in animal lens. Specific aims include the following topics: (1) selective triggering of transglutaminase- mediated cross-linking in lens--evaluation of competitive and non- competitive inhibitors; (2) N epsilon-(gamma-glutamyl) lysine in the cross-linked beta crystallin dimers; (3) identification and isolation of protein targets of transglutaminase in lens by labelling with dansylcadaverine and using anti-dansyl antibody affinity procedures--application for assessing protein associations; (4) sequencing of amino acids near the transglutaminase-reactive glutaminyl residues of beta crystallin subunits; (5) interactions of soluble proteins of the lens with dansylcadaverine-labelled beta crystallin subunits, assessed by changes in fluorescence; (6) N epsilon-(gamma-glutamyl) lysine in cross-linked polymers of human cataracts--heterogeneity, analysis of composition by immunological means and cross-link frequency; (7) N epsilon- (gamma-glutamyl) lysine content of beta crystallin dimers in aging human lens and (8) regulations of lens transglutaminase.